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(11) | EP 1 536 492 A2 |
(12) | EUROPEAN PATENT APPLICATION |
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(54) | Electroluminescent element and lighting unit |
(57) In an electroluminescent element, a first electrode having first and second opposite
surfaces is layered on a substrate so as to contact the substrate on its first surface.
A luminescent layer containing a light-emitting layer is layered on the first electrode
so as to contact the second surface of the first electrode. A second electrode having
first and second opposite surfaces is layered on the luminescent layer so as to contact
the luminescent layer on its first surface. The second surface of the second electrode
is at least partially exposed. A first terminal is provided on the second surface
of the first electrode at a portion that does not contact the luminescent layer. A
second terminal is partially formed in the exposed portion. At least one of the first
and second electrodes is transparent. The first and second terminals are connected
to a power source. |
BACKGROUND OF THE INVENTION
SUMMARY OF THE INVENTION
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a schematic cross-sectional view of an organic electroluminescent element according to a first preferred embodiment of the present invention;
FIG. 1B is a schematic front end view of the organic electroluminescent element according to the first preferred embodiment of the present invention;
FIG. 2A is a schematic view showing one aspect of a manufacturing process of the organic electroluminescent element according to the first preferred embodiment of the present invention;
FIG. 2B is a schematic view showing another aspect of the manufacturing process of the organic electroluminescent element according to the first preferred embodiment of the present invention;
FIG. 2C is a schematic view showing yet another aspect of the manufacturing process of the organic electroluminescent element according to the first preferred embodiment of the present invention;
FIG. 3A is a schematic cross-sectional view of an organic electroluminescent element according to a second preferred embodiment of the present invention;
FIG. 3B is a schematic front end view of the organic electroluminescent element according to the second preferred embodiment of the present invention;
FIG. 4A is a schematic back side view of a lighting unit according to a third preferred embodiment of the present invention; and
FIG. 4B is a schematic cross-sectional view of the lighting unit according to the third preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
(1) The non-covered portion of the cathode 5 which is not covered with the sealing
layer 6 forms the cathode terminal 8.
Since the entire surface of the opposite surface 51 of the cathode 5 is not covered
with the sealing layer 6, and only its periphery is covered with the sealing layer
6, the exposed portion, which is not covered with the sealing layer 6, is used as
the cathode terminal 8, and is connected to an external power source. Accordingly,
since the cathode terminal 8 may be provided on an opposite side of a light output
side of the organic EL element 1, while the cathode terminal 8 need not be provided
on a portion other than the portion of the substrate 2 where the organic layer 4 is
provided, the area of the substrate 2 for the same area of the organic layer 4 may
be reduced. In other words, the area contributing to light emission may be increased
in the area of the substrate 2.
(2) The cathode 5 has an airtightness.
Since the cathode 5 has a thickness of 0.5 µm or above, the cathode 5 has a sufficient
airtightness. That is, the cathode 5 prevents a substance such as moisture and oxygen
from degrading the organic layer 4 by entering into the organic EL element 1 through
the cathode 5. Therefore, even if the entire surface of the opposite surface 51 of
the cathode 5 is not covered with the sealing layer 6, and the exposed portion, which
is not covered with the sealing layer 6, is used as the cathode terminal 8, the organic
EL element 1 is prevented from degrading due to moisture or oxygen entering from the
outside and shortening the life thereof.
(3) The organic layer 4 is not exposed.
After the organic layer 4 is formed to contact the anode 3, the cathode 5 is formed
to contact the entire surface of the opposite surface 42 of the organic layer 4. Since
the sealing layer 6 is deposited on that basis, the sealing layer 6 seals the entire
portion, other than the surface 41 and the surface 42. Accordingly, the organic layer
4 is covered on its outer surface with the anode 3, the cathode 5 and the sealing
layer 6, so that there is no exposed portion. Therefore, degradation of the organic
layer 4 due to entry of moisture or oxygen is prevented.
(4) The organic EL element 1 emits white light.
The light-emitting layer of the organic layer 4 is constituted of a layer for emitting
green light, a layer for emitting blue light and a layer for emitting red light. As
voltage is applied to the organic EL element 1, these layers simultaneously emit light
thereby emitting white light as a whole. Since the white light emitted from the organic
EL element 1 has peaks in a red color spectral range, a blue color spectral range
and a green color spectral range, clear color is generated when displaying an image
through an RGB color filter.
(5) Utilization rate of light is high.
An aluminum thin film having a light reflectivity is employed as the cathode 5.
Therefore, light-traveling from the light-emitting layer to the cathode 5 is reflected
toward the substrate 2 on the cathode 5, and the reflected light is partially emitted
outside from the substrate 2. Accordingly, in comparison to the cathode 5 made of
a material having no light reflectivity, more light that is emitted from the light-emitting
layer is emitted from the substrate 2.
A second preferred embodiment of the present invention will now be described with
reference to FIGS. 3A and 3B. The second preferred embodiment is different from the
first preferred embodiment in that the positions of the anode terminal 9 and the cathode
terminal 8 are different. The same reference numerals denote the substantially identical
components to those of the first preferred embodiment, and portions different from
the first preferred embodiment will mainly be described. It is noted that a slanted
line for indicating cross-section is partially omitted. For easier recognition, the
same components are indicated with the same slanted lines and the like, irrespective
of a cross-sectional view and a front end view in FIGS. 3A and 3B.
In the organic EL element 1 according to the second preferred embodiment, the non-contact
portion 32 with the organic layer 4 is only provided along one side of the anode 3.
The sealing layer 6 is formed to cover substantially half (the right half in FIG.
3A) of the opposite surface 51 of the cathode 5. As shown in FIGS. 3A and 3B, the
anode terminal 9 is formed to extend from the non-contact portion 32 of the anode
3 to the portion where the sealing layer 6 covers the opposite surface 51 of the cathode
5.
The cathode terminal 8 is provided to contact the non-covered portion 51 of the opposite
surface of the cathode 5, which is not covered with the sealing layer 6. The surface
of the anode terminal 9 and the surface of the cathode terminal 8 are included in
the substantially same plane.
Such an organic EL element may be manufactured as follows. That is, in a manufacturing
process of the anode terminal 9, similar to the manufacturing method described for
the first preferred embodiment, aluminum is vapor-deposited on the non-covered portion
51 of the cathode 5, which is not covered with the sealing layer 6, without screening
by a mask. As manufactured above, the anode terminal 9 and the cathode terminal 8
are formed at the same time.
According to the second preferred embodiment, in addition to the advantageous effects
(1) through (5) of the first preferred embodiment, the following advantageous effects
are obtained.
(6) The anode terminal 9 and the cathode terminal 8 are arranged in line.
The anode terminal 9 is provided to contact the surface of the sealing layer 6
on the side opposite to the cathode 5, to cover a portion of the cathode 5, which
is covered by the sealing layer 6. Therefore, the anode terminal 9 may be arranged
in line with the cathode terminal 8. As the anode terminal 9 and the cathode terminal
8 are arranged in line, the cathode terminal 8 is not surrounded by the anode terminal
9 in the same manner of the first preferred embodiment, so that there is increased
flexibility for wiring arrangements from the power source to both the terminals.
(7) The surface of the anode terminal 9 and the surface of the cathode terminal 8
are included in the substantially same plane.
The anode terminal 9 is formed while the cathode terminal 8 is formed on the non-covered
portion 51 of the cathode 5 which is not covered with the sealing layer 6. Accordingly,
unlike in the case of providing a mask on the portion 51, the surface of the anode
terminal 9 and the surface of the cathode terminal 8 are arranged on the substantially
same plane.
A third preferred embodiment of a lighting unit 200 according to the present invention
will now be described with reference to FIGS. 4A and 4B. FIG. 4A is a schematic backside
view of the lighting unit 200 according to the third preferred embodiment. FIG. 4B
is a cross-sectional view that is taken along the line I-I in FIG. 4A.
As shown in FIG. 4A, the lighting unit 200 is formed by arranging the organic EL elements
1 of the second preferred embodiment in a two-by-two matrix. Each anode terminal 8
of the organic EL elements 1 is connected to a positive electrode 201 of the lighting
unit 200, and each cathode terminal 9 is connected to a negative electrode 202 of
the lighting unit 200. All organic EL elements 1 are fixed to each other by a frame
(not shown). The positive electrode 201 and the negative electrode 202 are fixed to
a base 203. Additionally, a positive terminal 204, which is electrically connected
to the positive electrode 201, and a negative terminal 205, which is electrically
connected to the negative electrode 202, are provided along one side of the base 203.
It is noted that the outline of the base 203 which should be indicated by a solid
line is indicated by a dotted line, and the outlines of the organic EL elements 1,
the anode terminal 8, the cathode terminal 9, the positive electrode 201, and the
negative electrode 202, which should be indicated by dotted lines, are indicated by
solid lines in FIG. 4A for easier recognition.
A manner of electrical connection between the anode terminals 8 of the organic EL
elements 1 and the positive electrode 201 of the lighting unit 200 and a manner of
electrical connection between the cathode terminals 9 of the organic EL elements 1
and the negative electrode 202 of the lighting unit 200 will now be described.
As shown in FIG. 4A, two of four organic EL elements 1 are arranged so that the respective
anode terminals 8 are arranged on one line, and the respective cathode terminals 9
are arranged on one line. There are two pairs of the organic EL elements 1 and these
pairs are in contact with each other.
The positive electrode 201 of the lighting unit 200 includes two branches 201a connected
to the anode terminals 8 of the organic EL elements 1 and a trunk 201b connected to
the positive terminal 204 for connecting these two branches 201a. One branch 201 a
is arranged to connect two anode terminals 8, which are inline with each other.
Likewise, the negative electrode 202 of the lighting unit 200 includes two branches
202a connected to the cathode terminals 9 of the organic EL elements 1 and a trunk
202b connected to the negative terminal 205 for connecting these two branches 202a.
One branch 202a is arranged to connect two cathode terminals 9, which are in line.
Accordingly, all organic EL elements 1 are electrically arranged in a parallel relation
to each other.
The operation of the lighting unit 200 will now be described.
As voltage is applied between the positive terminal 204 and the negative terminal
205 of the lighting unit 200, voltage is applied between the anode terminal 8 and
the cathode terminal 9 of each organic EL element 1 through the positive electrode
201 and the negative electrode 202. Then, voltage is simultaneously applied between
the anode terminals 8 and the cathode terminals 9 of all organic EL elements 1, so
that all the organic EL elements 1 simultaneously emit light.
According to the third preferred embodiment, the following advantageous effects are
obtained.
(8) A lighting unit formed by plural lines of the organic EL elements 1 is obtained.
Since all organic EL elements 1 are electrically connected in parallel with each
other in the lighting unit 200, as voltage is applied between the positive terminal
204 and the negative terminal 205, all organic EL elements 1 simultaneously emit light.
Since these organic EL elements 1 are arranged to contact each other, almost all portions
of the organic EL elements 1 in the lighting unit 200 emits light due to the simultaneous
light emission of the organic EL elements 1, thereby becoming a large lighting unit
as a whole. As the plural organic EL elements 1 are arranged and simultaneously emit
light to form a lighting unit, which is larger than each organic EL element 1, a yield
rate as a product is raised in comparison to a large lighting unit formed by a single
organic EL element 1 having the same size.
(9) The organic EL elements 1 forming the lighting unit 200 are easily replaced.
The organic EL elements 1 forming the lighting unit 200 are connected to the electrodes
(the positive electrode 201, the negative electrode 202) of the lighting unit at the
opposite surface to the surface through which light is emitted. Therefore, when some
of the organic EL elements 1 forming the lighting unit 200 fail or are degraded, such
organic EL elements 1 may easily be removed and new organic EL elements 1 may easily
be inserted into the lighting unit 200.
(10) Even if some of the organic EL elements 1 forming the lighting unit 200 are electrically
disconnected, the remainder of the organic EL elements 1 continue to emit light.
Since all organic EL elements 1 forming the lighting unit 200 are electrically
connected in parallel with each other, even if some of them are electrically disconnected,
there is no possibility that all organic EL elements 1 stop emitting light, as compared
to an arrangement in which all organic EL elements 1 are electrically connected in
series. Accordingly, even if one organic EL element 1 is not in contact with the electrodes
of the lighting unit, the other organic EL elements 1 continue to emit light.